Collagen fibers are essential components of bone, cartilage and blood vessels. The fibers are composed of collagen molecules and these are manufactured by connective tissue cells. The cells make a larger molecule, called procollagen, which is converted to collagen. The object of this proposal is to find out how procollagen is assembled within the cell, modified by the cell and upon secretion converted to collagen and forms collagen fibers. Particular interest is paid to the necessary interactions between certain regions of the component polypeptide chains of the procollagen molecule. These regions, called registration peptides, assure the smooth assembly of the molecule and facilitate subsequent folding of the components. The significance of this work lies in our need to make collagen fibers for the healing of surgical wounds and in normal growth and development. Abnormalities occur in several connective tissue and cardiovascular diseases and knowledge of the normal assembly processes of these fibers should help our understanding of the pathological aberrations. BIBLIOGRAPHIC REFERENCES: Morris, N.P., Fessler, L.I., Weinstock A., and Fessler, J.H., "Procollagen Assembly and Secretion in Chick Bone," J. Biol. Chem. 250, 5719-5726, (1975). Fessler, J.H., and Tandberg, W.D., "Interactions Between Collagen Chains and Fiber Formation," J. Supramolecular Structure. (1975) 3: 17-32.